April 17 2020: Aarogya Setu , the Indian government app  to help track the spread of Covid-19 has reached 50 million users in just 13 days-fastest ever globally for an app -- but some security concerns have been expressed.
Tweeted NITI Aayog CEO Amitabh Kant: "Telephone took 75 years to reach 50 milion users, radio 38 yrs,television 13 yrs,Internet 4 yrs, Facebook 19 months, Pokemon Go 19 days. #AarogyaSetu,India’s app to fight COVID-19 has reached 50 mn users in just 13 days-fastest ever globallyfor an App. Salute the spirit of India!"
Developed by the National Informatics Centre of the Ministry of Electronics and IT, Aarogya Setu  is available for  both Android and iOS smartphones  and supports 11 languages
Prime Minister Modi urged the citizens to download the application in order to keep themselves safe during the pandemic outbreak. It is possible to use it as an e-pass to facilitate travel from one place to another said PTI.The app uses your location to know of the area you are around comes under the infected areas of the database and also needs an activated Bluetooth to determine if you have been within six feet from the infected person..
However concerns have been expressed by privacy advocates: “The Aarogya Setu application appears to clearly be inconsistent with privacy-first efforts which are being considered by technologists and governments,” wrote Sidharth Deb of the  Internet Freedom Foundation, in a paper. Vague language in Aarogya Setu’s privacy agreement leaves it open for the government to repurpose this data for its other agencies, the paper suggested, adding that the committee that designed India’s app “lacks any representation from the ministry of health and family welfare, or any independent involvement of persons with a medical or epidemiological background.”
A week after the launching the app, the government  updated the privacy policy of Aarogya Setu, addressing some but not all the concerns:
Deccan Herald, April 17 2020: Surveillance in health app clothing?
Economic Times: 'Aarogya Setu's not all that healthy for a person's privacy’
Medianama:  Comparing old and new privacy policies 
NDTV: NitiAayog defends  Aarogya Setu